The CB whip is about the same length as the supplied wire antenna..thus it will tune to it, H or V position as with the wire antenna.
You can also crimp a spade connector to the end of that whip and mount directly to the stub.
RFB
I noted the wire length similarity and took what @mram1500 recommended and tried it.
Unsure who else has done this. I hadn't seen/confirmed anyone having done this before.
Hopefully it continues working/tuned and range is sufficiently better when mounted outdoors.
Hope others see this in the future and get moving over the big hurdle of the TH units and the external ATU expense.
You can tune a CB whip, mounted on top of a weatherproof box with the TH inside the box. I did a similar thing with an AMT3000. It will work. My range with the AMT3000 was around 1/4 mile, you'll probably get similar range with the Talking House (I've found those 2 transmitters comparable, except the AMT3000 can sound better due to its audio processing).
However, the only real advantage the Talking House has over some of the other transmitters, such as the ProCaster, Rangemaster, etc. is the ATU, which allows it to get comparable range while keeping the transmitter indoors in a weather controlled environment. Otherwise, unless there are pressing reasons to go with the TH (i.e., you already have one, budget constraints, etc.), I'd go with something else mounted outdoors.
And something to think about - the cost of an ATU plus the Talking House (when you include the outrageous shipping) is roughly comparable to that of the Procaster, and the Procaster is a much better transmitter, which also gives you the option (at least with the newer ones) of using asymmetric processing using an Inovonics 222 or something similar.
But, putting the TH outside with a whip attached to the "wire" port should give the same result as having the TH inside and using the hard to find or expensive new ATU.
Of course, I prefer to have mine inside and got lucky finding a used ATU on Ebay for $99 plus shipping and I had to buy the whip.
But, for the low budget McGiver experience I wouldn't be opposed to doing temporary testing with the TH in an outside box with the whip mounted on top of the box.
I believe Lefty may have tried this.
Actually, the Talking House outside with a whip wouldn't generate the same results as with the ATU, because the coax that connects the ATU probably does radiate. It's legal, because the two are FCC certified for use together, but that's also why the TH ATU would likely not be legal for use with any other transmitter (for which it has not been certified for use with).
Well, assuming in both cases, ATU or simple whip, these are both ground mounted with adequate RF ground under the antenna I wouldn't think there would be much difference.
If the coax does radiate then yes a long run of coax would cause an increase in signal especially if the ATU is elevated so that you have a vertical run of coax.
If the system is designed correctly the coax should not radiate but who knows for sure without some empirical testing.
I'm guessing that the ATU also may have lower loss coils than the smaller motorized coil inside the transmitter. Also, ATU antenna has more flexibility in antenna placement (higher and away from the building).
" It's legal, because the two are FCC certified for use together, but that's also why the TH ATU would likely not be legal for use with any other transmitter (for which it has not been certified for use with)."
Combined they are legal to use together. However I doubt that it would not be legal to use the ATU with some other transmitter if the other transmitter were directly below the ATU unit and no coax used, or another ATU design used with the TX..again directly connected without a coax. The only legal use of either the TH TX and ATU with the coax is using them combined.
The real questions was NEVER about if those two devices were legal to use together or not. The question WAS how was that ATU mounted when it was certified...as high as the 25 foot coax..or like all the other certified units were tested sitting on a 1 meter high table in a testing chamber over a ground system.
RFB
You can tune a transmitter but you can't tuna fish.
The question WAS how was that ATU mounted when it was certified...as high as the 25 foot coax..or like all the other certified units were tested sitting on a 1 meter high table in a testing chamber over a ground system.
I can answer that. The antenna that is used at the AM frequencies is a magnetic loop mounted on a 1 meter high tripod. To measure harmonics, the antenna, most likely a biconical, is moved up and down on a 3 meter mast and observations are made in the vertical and horizontal plane. That being said, the ATU was placed on a 1 meter insulated test bench and the 25 feet of coax was most likely couild and laying on the table. The transmitter had a 1 meter ground wire attached to the ground plane under the test bench.
Hope this helps.
"Hope this helps."
As I pointed out before...testing done like all the other certified units in those testing chambers.
Hope that settles that matter.
RFB
Ah, you're right. Missed that.
I would surmise that if the FCC approves of that testing methodology and issues a certification number for a transmitter, then it must be OK. I guess it's a little bit of do as I say, not as I do.
mram1500 said:
"If the system is designed correctly the coax should not radiate..."
This subject has been discussed before, but I'll cover it again to hopefully make it a clearer.
A vertical monopole antenna REQUIRES a ground wire to function as an antenna. Like any electrical circuit, the RF current in the antenna (which causes radiation) needs a closed circuit path. The path is from the antenna, through the air, to the ground and returning back to the ATU. The current in the ground is also referred to as the "displacement current" because the path through the air is equivalent to a small capacitance between the antenna element and ground. Because this is a closed loop, the current flowing into the bottom of the antenna element is equal to the return current flowing in the ground wire. The displacement current depends on the ground resistance. High ground resistance will reduce the current, and low ground resistance will increase the current. Thus, the signal radiation is higher with lower ground resistance.
If the ATU is grounded locally with a ground rod and radial system, the RF current will divide between the local-ground wire and the coax shield. Likely most, but not all of the current will flow in the local-ground wire. If the ATU is not grounded locally, ALL of the RF ground current flows over the coax shield.
When the ATU is grounded locally and the COAX is laying on the earth, or buried, the coax shield acts as one radial, or one of many radials if a radial system is used, so any current flowing on the coax shield will be part of the ground system and won't radiate. The effectiveness of the coax as a one-wire radial will depend on the length of the portion of coax laying on the earth. Longer would be better.
When the ATU is elevated, the vertical portion of the local-ground wire (if present) and the vertical portion of the coax will radiate because of the RF displacement current flowing in each. If no local-ground wire is present, all of the RF displacement current will flow on the coax shield.
The RF displacement current flowing on the outside of the coax shield is not in the same electrical circuit as the RF current flowing inside the coax from the transmitter. The "inside" coax current does not cause radiation because it is balanced between the center conductor and the inside of the shield.
I agree that common mode current can flow along the outside of the coax shield. And, this common mode current will cause radiation from the coax shield. Common mode current exists because the terminal load is not proper.
A center fed dipole antenna is a balanced antenna, one half of the antenna on either side of the feed point. But, if it is fed in an unbalance manner, as with coax, there will be common mode currents that flow along the outside of the shield. This among other things skews the radiation pattern due to radiation from the shield. By properly feeding the antenna with a balun which converts an unbalanced feedline to a balanced feed at the antenna the common mode currents are minimized or eliminated. In this case the antenna has the upper and lower portions Phil refers to.
There are antennas designed to operate without a ground, fed by coax and do not suffer from common mode currents. The most commonly used is the half wave, end fed dipole. Again a common mode balun (choke) is placed at the proper point on the coax, one half wave length from the end of the antenna. One half of the antenna is the upper part of the dipole, the shield is the lower part of the dipole. Without the balun, common mode current would flow along the entire coax and cause RF hot spots along the coax and would radiate. With the balun, common mode currents are minimized or stopped at the balun and no radiation beyond the balun back to the transmitter occurs.
Another common antenna made for CB radios is a half wave monopole with a matching network in the base and no radials. When the matching network is properly tuned, the antenna radiates but no common mode current flows along the coax, no radiation from the coax.
So, there are antennas that operate without a ground and the coax does not radiate as the proper termination minimizes or stops the common mode current which otherwise would cause radiation from the outside of the coax shield.
When I run a field strength meter along the length of my ATU coax, there is no detectable RF radiating from the coax.
I posted a link to an article from a radio magazine some time ago reference the end fed dipole. I built one. It works. There are no RF hot spots on the coax which occur when common mode currents flow along the outside of the coax shield.
Since this thread drifted off topic and was not making constructive progress several posts were deleted. Let's stay on topic for the original post.
Neil